1. Technical Field
The present invention relates to electromagnetic interference shielding, and in particular to electromagnetic interference shielding for electronic devices. More specifically, the present invention relates to an electromagnetic interference shielding assembly for use between electronic devices.
2. Description of the Related Art
It is critical today to shield electronic equipment, such as computers, against electromagnetic interference (EMI) emissions. In the past, computer products contained slower processors. Consequently, the problem of escaping emissions of these types through openings in computer enclosures was not significant. But the advance of faster processors and switching has changed this situation. While increased processing speeds have made remarkable improvements in performance and proficiency, EMI containment problems have been exacerbated.
Today, it is not uncommon for computers to employ clock speeds in the range of 50 to 200 MHz or more. Furthermore, digital circuits operating at these high frequencies may have pulse rise times of a nanosecond or less. These high speeds can cause EMI to be radiated at harmonic frequencies in excess of one GHz.
The Federal Communications Commission ("FCC") has established standards that limit the amount of allowable EMI emissions from electronic devices. To meet FCC emissions standards it is necessary to seal around expansion slots holding electronic modules cards and to seal around slots covered by blanks when these slots are not being used. In addition, commercial pressure exists to compact the spacing between expansion slots or openings.
To attenuate EMI, electronic modules need to be more properly grounded around their perimeter. The electronic modules are typically packaged next to one another with grounding springs between the modules being required. Installing springs on the electronic modules requires special module handling requirements as the delicate grounding springs are easily damaged. One method employed to avoid this damage is to mount grounding springs directly to the chassis, which supports the module. See U.S. Pat. No. 4,780,570. Chassis mounted springs also eliminate the need to modify or retrofit previously assembled modules. The main problem with the chassis mounted spring is that very little space is available for mounting them. Electronic modules are typically placed very close to one another, and consequently very little room is available for an EMI grounding spring that can maintain it's shape and function. Therefore, it would be advantageous to have an improved EMI grounding spring that fits between modules and maintains its shape and function.